Question about the tank lid design of UltraMax

We are looking to replace 2 toilets in our home. We like the one piece design of the UltraMax and it appears to be a good one (flushability) from the reviews I've read (never realized there was such a big difference and so many choices), but am thinking the top lid of the tank appears to have a downward slope, higher toward the back of the lid and lower toward the front?
Can anyone that has this toilet tell me if anything can be placed on the tank lid without it sliding off? Are the pictures deceiving me?
Without going into detail: This is an important factor for a family member who is wheelchair bound.

We'll need the tank to hold a few things so I guess the UltraMax won't work out for us.
The ADA toilets are not good for us. Something we found out about experiencing life with SCI (low level quadriplegic)...ADA toilets are great for people that have trouble with their knees or their back but are able to stand. A paralyzed person who is unable to stand needs their feet to reach the floor to give them stability. The grab bar on the wall helps but with little grip he couldn't stop himself from falling if he became unbalanced.
A special padded (2" padding to help prevent a pressure sore) raised (height adjustable) toilet/shower chair has to be used over a toilet. Plus a space (approx. 3") is needed in between the toilet and this special chair. Even with a regular height toilet, we still have to use a foot stool. The transfer is very difficult and dangerous when we stay in a hotel and have to use the ADA height toilet
I'm thinking that we will be happy with the regular height Drake elongated model.
Thanks so much for this site. It is very informative!